Method for fabricating liquid crystal phase modulation device having spacer in liquid crystal layer

ABSTRACT

A method for fabricating a liquid crystal phase modulation device is provided. The method includes detecting thicknesses of a plurality of portions of a reference liquid crystal layer of a reference liquid crystal phase modulation sample; determining a distribution according to the thicknesses of the portions of the reference liquid crystal layer; forming a plurality of spacers over a first substrate in the determined distribution; and combining the first substrate with a second substrate and a liquid crystal layer to form the liquid crystal phase modulation device.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional application of U.S. patent applicationSer. No. 16/163,592, filed Oct. 18, 2018, which is herein incorporatedby reference in its entirety.

BACKGROUND Field of Invention

The present disclosure relates to a method for fabricating a liquidcrystal phase modulation device.

Description of Related Art

Electrically tunable optical phase modulator includes an optoelectronicmaterial layer (i.e., liquid crystal material) having refractive indextunable based on the electric field. By designing suitable shapes ofelectrodes, when a specific voltage(s) is applied thereon, a phasedifference distribution of the optoelectronic material layer can be madeto realize various optical effects. For example, the optoelectronicmaterial layer can imitate an optical element, such as a lens, agrating, and a switch.

SUMMARY

In some embodiments of the present disclosure, spacers are distributedin response to the bending of the substrate, so as to keep a cell gap ofa liquid-crystal device uniform. Furthermore, the spacers are designedto have a shape less influencing a rubbing procedure, such that a rubbedalignment layer can effectively align the liquid crystal molecules.

According to one embodiment of the present disclosure, A method forfabricating a liquid crystal phase modulation device is provided. Themethod includes detecting thicknesses of a plurality of portions of areference liquid crystal layer of a reference liquid crystal phasemodulation sample; determining a distribution according to thethicknesses of the portions of the reference liquid crystal layer;forming a plurality of spacers over a first substrate in the determineddistribution; and combining the first substrate with a second substrateand a liquid crystal layer to form the liquid crystal phase modulationdevice.

According to one embodiment of the present disclosure, A method forfabricating a liquid crystal phase modulation device is provided. Themethod includes fabricating a reference liquid crystal phase modulationsample by combining a first reference substrate, a second referencesubstrate, a reference sealant, and a reference liquid crystal layer;detecting thicknesses of a plurality of portions of the reference liquidcrystal layer of the reference liquid crystal phase modulation sample;determining a distribution according to the thicknesses of the portionsof the reference liquid crystal layer; forming a plurality of firstspacers over a first substrate in the determined distribution; andcombining the first substrate, a second substrate, a device sealant, aliquid crystal layer to form the liquid crystal phase modulation device,wherein the device sealant has a thickness substantially equal to athickness of the reference sealant.

It is to be understood that both the foregoing general description andthe following detailed description are by examples, and are intended toprovide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 is a flow chart of a method for fabricating a liquid crystalphase modulation device according to some embodiments of the presentdisclosure;

FIG. 2A is a system for fabricating a liquid crystal phase modulationdevice according to some embodiments of the present disclosure;

FIG. 2B illustrates operations of a computing device according to someembodiments of the present disclosure;

FIGS. 3A-3G illustrate intermediate stages of a method for fabricating aliquid crystal phase modulation device according to some embodiments ofthe present disclosure;

FIGS. 4A-4C illustrate intermediate stages of a method for fabricating aliquid crystal phase modulation device according to some embodiments ofthe present disclosure;

FIG. 5 is a schematic cross-sectional view of a liquid crystal phasemodulation device according to some embodiments of the presentdisclosure;

FIG. 6 is a schematic cross-sectional view of a liquid crystal phasemodulation device according to some embodiments of the presentdisclosure; and

FIGS. 7A and 7B are a schematic top view of a spacer in a liquid crystalphase modulation device according to some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are used in thedrawings and the description to refer to the same or like parts.

FIG. 1 is a flow chart of a method 100 for fabricating a liquid crystalphase modulation device 400 according to some embodiments of the presentdisclosure. FIG. 2A is a system 200 for fabricating a liquid crystalphase modulation device 400 according to some embodiments of the presentdisclosure. FIGS. 3A-3G illustrate intermediate stages of a method forfabricating the liquid crystal phase modulation device 400 according tosome embodiments of the present disclosure. The illustration is merelyexemplary and is not intended to be limiting beyond what is specificallyrecited in the claims that follow. It is understood that additionaloperations may be provided before, during, and after the operationsshown by FIG. 1, and some of the operations described below can bereplaced or eliminated for additional embodiments of the method. Theorder of the operations/processes may be interchangeable.

Referring to FIG. 1 and FIG. 3A, the method 100 begins at step 102 wherea substrate 310 is provided. Herein, the substrate 310 includes a basesubstrate 312, plural electrodes 314 over the base substrate 312, adielectric layer 316, and an alignment layer A1 thereon. The basesubstrate 312 may be rigid and/or flexible substrates. For example, thebase substrate 312 is made of suitable transparent insulating materials,such as glass, quartz, or polymeric material. The electrodes 314 may bemade of suitable transparent conductive materials, such as indium tinoxide (ITO) or antimony tin oxide (ATO). The dielectric layer 316 ismade of silicon oxide, polymer, or other suitable dielectric material.The alignment layer A1 may be made of polyimide.

Referring to FIG. 1 and FIG. 3B, the method 100 proceeds to step 104where a reference liquid crystal phase modulation sample 300 isassembled. To be specific, the reference substrate 310, a substrate 320,a liquid crystal layer 330, and a reference sealant 340 are combined toform the reference liquid crystal phase modulation sample 300. Thesubstrates 310 and 320 are opposite to each other. The liquid crystallayer 330 is between the substrates 310 and 320. The reference sealant340 is between the substrates 310 and 320 and surrounds the liquidcrystal layer 330. The sealant 340 is designed to have a desiredthickness for spacing the substrates 310 and 320 from each other, andallowing the liquid crystal layer 330 therebetween to have acorresponding thickness enough to realizing phase modulation, such aslens effect. For example, the thickness of the sealant 340 may be in arange of about 10 micrometers to about 50 micrometers. In someembodiments, a thinning process may be performed to thin the basesubstrate 312 of the substrates 310 or a base substrate 322 of thesubstrates 320. In some embodiments, after the assembly, a chippingprocess may be performed.

Herein, the substrate 320 includes a base substrate 322, an electrodelayer 324 over the base substrate 312, and an alignment layer A2thereon. The base substrate 322 may be rigid and/or flexible substrates.For example, the base substrate 322 is made of suitable transparentinsulating materials, such as glass, quartz, or polymeric material. Theelectrode layer 324 may be made of suitable transparent conductivematerials, such as indium tin oxide (ITO) or antimony tin oxide (ATO).The alignment layer A2 may be made of polyimide. The alignment layer A2may be rubbed in an alignment direction according to the alignmentdirection AD1 of the alignment layer A1. For example, the alignmentdirection of the alignment layer A2 may be parallel with the alignmentdirection AD1 of the alignment layer A1 for a parallel-aligned (PA)liquid crystal configuration. In some other examples, the alignmentdirection of the alignment layer A2 may be orthogonal to the alignmentdirection AD1 of the alignment layer A1 for a twisted nematic (TN)liquid crystal configuration.

In some embodiments, due to the thin substrates, the large cell gap, andthe large area of the reference liquid crystal phase modulation sample300, the substrates 312 and 322 may bend and the cell gap between thesubstrates 312 and 322 (e.g., the thickness of the liquid crystal layer330) may vary at different positions. The bonding of the substrates 312and 322 may further enhance the non-uniformity of the cell gaptherebetween. FIG. 3C is a top view of the reference liquid crystalphase modulation sample 300 of FIG. 3B. For example, in FIG. 3C, thethicknesses of plural portions 332 of the liquid crystal layer 330 atplural various positions P may be different.

Reference is made to FIG. 1, FIG. 2A and FIGS. 3B and 3C. The method 100proceeds to step 106 where the reference liquid crystal phase modulationsample 300 is detected, so as to obtain thicknesses T of the portions332 of the liquid crystal layer 330 at positions P. To specific, thesystem 200 has a detecting apparatus 210 capable of detecting opticalproperties of the reference liquid crystal phase modulation sample 300at plural various positions P. By analyzing the detected opticalproperties of the reference liquid crystal phase modulation sample 300at plural various positions P, the thicknesses T of portions 332 ofliquid crystal layer 330 at the various positions P are obtained.

In the present embodiments, the detected positions P are uniformlydistributed and spaced by the same distance. In some other embodiments,the detected positions P may be arranged in a different way, such asrandom distribution. According to the detecting apparatus 210, theportions 332 may be detected time-sequentially or simultaneously. Insome embodiments, for example, the detecting apparatus 210 may be aspectrometer, a spectrophotometer, or other suitable apparatus. In someembodiments, the sealant 340 is detected by suitable optical microscopeprior to detecting the thicknesses of the portions 332, and the positionof the sealant 340 is marked. The marked position of the sealant 340 mayserve as a reference with respect to the positions of portions 332during detecting the thickness of the portions 332. For example,positions of the inner edges E1 and E2 of the sealant 340 are marked.

The method 100 proceeds to step 108 where a distribution of spacers tobe formed is determined according to the detected thicknesses T of theplural portions 332 of the liquid crystal layer 330. For example, thesystem 200 includes a computing device 220 connected to the detectingapparatus 210. In some embodiments, the computing device 220 includes aprocessor, memory, and an interface. For example, the computing device220 may be a single computer or a distributed computer. The computingdevice 220 receives information (e.g., a signal) of the detectedthicknesses T and detected positions P from the detecting apparatus 210and performing statistical analysis processes, so as to obtain thedistribution of spacers to be formed. In some embodiments, the computingdevice 220 includes one or more software programs for calculating thedata.

FIG. 2B illustrates operations 222-229 of the computing device 220according to some embodiments of the present disclosure. Reference ismade to FIG. 2A and FIG. 2B. To be specific, at calculation operation222, thickness differences TD, horizontal distances FDX, and verticaldistances FDY at the detected positions P are obtained by calculatingthe positions P and the detected thickness T. In the presentembodiments, at one of the positions P, the thickness difference TD isreferred to as the difference between a desired thickness of the liquidcrystal layer 330 and the detected thickness T of the liquid crystallayer 330 at said one of the positions P in FIG. 3B. The horizontaldistance FDX is referred to as a distance between said one of thepositions P and an edge E1 of the sealant 340 in FIG. 3C. The verticaldistance FDY is a distance between said one of the positions P and anedge E2 of the sealant 340 in FIG. 3C.

Subsequently, the computing device 220 builds a relationship between thedistances FDX/FDY and the thickness differences TD at the detectedpositions P, for example, by a fitting operation 224. In someembodiments, the relationship is linear and described in formula (a):TD _(i) =a×FDX _(i) +bTD _(i) =a×FDY _(i) +bWhere a and b are parameters, and i is a positive integral indicatingthe number of the positions of the liquid crystal layer 330 to be count.Through the relationship, the thickness differences TD; of the liquidcrystal layer 330 at any positions (e.g., positions with distances FDX;and/or FDY; from the sealant 340) can be simulated and obtained. As theabove definitions, the thickness difference TD_(i) is referred to as thedifference between the desired thickness of the liquid crystal layer 330and a simulated thickness of the liquid crystal layer 330, and distancesFDX_(i) and/or FDY_(i) is referred to as a distance between thesimulated position and an edge E1/E2 of the sealant 340 in FIG. 3C.

Then, a primary factor operation 226 is performed for finding primaryfactors PF_(i). The primary factors PF_(i) are used to describe localvariation of the densities of spacers to be formed. It is designed thatdensities of spacers to be formed is proportional to a reciprocal of thethickness differences TD_(i) in some examples. For example, herein, theprimary factors PF_(i) may be described by the formula (b), based on aratio of the thickness differences TD_(i) and the maximum of thethickness differences TD_(i). For example, formula (b) is described as:

${PF_{i}} = {\left( \frac{TD_{i}}{\left( {TD_{i}} \right)_{\max}} \right)^{- 1} = \frac{\left( {TD_{i}} \right)_{\max}}{TD_{i}}}$

An adjustment operation 228 is performed for adjusting the primaryfactors PF_(i) by a parameter q, and thereby obtaining adjusted factorsAF_(i). The parameter q corresponds with the materials, dimensions, andthickness of the substrates (e.g. the base substrates). The parameter qis in a range of 0 to 1. For example, the parameter q is equal to 0.5.The adjustment may be described in formula (c):AF _(i) =PF _(i) +q×(100%−PF _(i))

Finally, a density operation 229 is performed. Herein, a desired densityD_(c) of spacers to be formed in a center position is determinedinitially, and then densities of spacers to be formed in other positions(e.g., positions with distances FDX_(i) and/or FDY_(i) from the sealant340) are determined by multiplying the desired density D_(c) by theadjusted factors AF_(i). Through the calculation, densities D_(i) inother positions (e.g., positions with distances FDX_(i) and/or FDY_(i)from the sealant 340) are obtained by formula (d). For example, theformula (d) is described as:D _(i) =D _(c) ×AF _(i)

In some embodiments of the present disclosure, an example is provided inTable 1, in which the desired density D_(c) of spacers to be formed inthe center position is determined as 10% initially. In some embodiments,the center position is about 17 millimeters away from the edge E1/E2.

TABLE 1 Distance FDX_(i)/FDY_(i) (millimeter) 2 7 12 17 Thicknessdifference TDi 0.2949 0.6553 1.0157 1.3761 Primary factor PFi 21%  48% 74% 100% adjusted factors AFi 60%  74%  87% 100% densities Di  6% 7.4%8.7%  10%

Through these operations, an uneven distribution of spacers to be formedis obtained. For example, the density of the spacers to be formeddegrades when approaching the edge E1/E2.

Reference is made to FIG. 1 and FIGS. 3D and 3E. FIG. 3E is across-sectional view taken along 3E-3E of FIG. 3D. The method 100proceeds to step 110 where spacers 450 are formed over a first substrate410 in the determined distribution. The first substrate 410 includes abase substrate 412, a first electrode layer 414, a dielectric layer 416,and an alignment layer A1. The dielectric layer 416 is formed over thefirst electrodes 414. The alignment layer A1 is formed over thedielectric layer 416. Herein, the first substrate 410 is provided withan active region AA and a seal region SA surrounding the active regionAA. In some embodiments, the active region AA may be designed accordingto customor's specification. In some embodiments, the active region AAand the seal region SA may have distances AX and AY therebetween,thereby preventing a sealant from being formed in the active region AA.For example, the distances AX and AY is in a range from about 200micrometers to about 1000 micrometers. In some other embodiments, theactive region AA may adjoin the seal region SA, and the distances AX andAY are substantially zero. The first electrode layer 414 is patterned toform first electrodes 414 a in the active region AA.

In the present embodiments, the spacers 450 are formed over thedielectric layer 416 in the determined distribution. To be specific, atpositions having distances FDX_(i)/FDY_(i) (referring to FIG. 2B) fromedges EX/EY of the seal region SA, the spacers 450 are formed to havethe density D_(i) (referring to FIG. 2B). For example, the firstsubstrate 410 has a first region R1 and a second region R2. In thehorizontal direction, the first region R1 is closer to the seal regionSA than the second region R2 is, and a density of the spacers 450 in thesecond region R2 is greater than a density of the spacers 450 in thefirst region R1. Through the configuration, the spacers 450 aredistributed unevenly.

Herein, the spacers 450 in the first region R1 are distributed unevenly.However, in some other embodiments, the spacers 450 in the first regionR1 may be distributed uniformly, the spacers 450 in the second region R2may be distributed uniformly, and the spacers 450 in the first region R1have a density lower than that of the spacers 450 in the second regionR2.

In some embodiments, the spacers 450 include a first spacer 450-1, asecond spacer 450-2, and a third spacer 450-3 arranged in a sequence.That is, the second spacer 450-2 is between and immediately adjacent tothe first spacer 450-1 and the third spacer 450-3. In the embodiments, adistance between the first spacer 450-1 and the second spacer 450-2 isdifferent from a distance between the second spacer 450-2 and the thirdspacer 450-3. For example, herein, the distance between the first spacer450-1 and the second spacer 450-2 is greater than the distance betweenthe second spacer 450-2 and the third spacer 450-3.

In some embodiments, the spacers 450 may be formed by a photolithographyapparatus 230 (referring to FIG. 2A), using suitable photolithographyand etching process. For example, an organic layer is formed on thefirst substrate 410. The organic layer is patterned using a mask toremove portions of the organic layer, the patterned organic layer formsa plurality of spacers 450 at least in the active region AA. In someembodiments, the organic layer may be made of positive photoresist ornegative photoresist. In some embodiments of the present disclosure, thespacers 450 are configured to maintain a cell gap. Herein, in theapplication of liquid crystal phase modulation (e.g., liquid crystallens), the spacers 450 may have a great height (e.g., 10 micrometers to50 micrometers), and the spacers 450 has a great width for maintainingitself on the substrate 410 steadily. For example, a width of thespacers 450 is greater than 5 micrometers.

Referring to FIG. 1 and FIG. 3F, the method 100 proceeds to step 112where a rubbing process is performed to the alignment layer A1. In someembodiments, a rubbing cloth 500 held by a roller is used to rub thealignment layer A1 in an alignment direction AD1. In some cases, becausethe large-sized spacers 450 may shelter some portions of the alignmentlayer A1, the portions of the alignment layer A1 may not be rubbed, suchthat the liquid crystal molecules over the portions of the alignmentlayer A1 may not lean in the alignment directions AD1.

In some embodiments of the present disclosure, referring to FIGS. 7A and7B, which illustrate schematic top views of one spacer 450, the spacers450 are designed to have a long axis LA in an alignment direction AD1.That is, spacers 450 extend along the alignment direction AD1. In someembodiments, as shown in FIG. 7A, the width of the spacer 450 narrows inthe alignment direction AD1. To be specific, the spacer 450 tapers alongthe alignment direction AD1. For example, the spacer 450 has edges 452Sinclined with respect to the alignment direction AD1 and a vertex of thetwo edges 452S. Through the configuration, the spacers 450 may shelterless area, and the alignment layer A1 is rubbed more effectively.

In some embodiments, as shown in FIG. 7B, the spacer 450 has portions452 and 454. The portion 452 faces the alignment direction AD1, whilethe portion 454 does not face the alignment direction AD1. To bespecific, the portion 452 has edges 452S facing the alignment directionAD1, and the portion 454 has edges 454S that does not face the alignmentdirection AD1. As illustrated in FIG. 7B, the portion 452 of the spacer450 tapers along the alignment direction AD1, and the edges 452Sinclines with respect to the alignment direction AD1. Through theconfiguration, the spacers 450 may shelter less area, and the alignmentlayer A1 is rubbed more effectively. Although the spacers 450 may bedesigned as shown in FIGS. 7A and 7B, it should not limit the scope ofthe present disclosure. In some other embodiments, the spacers 450 mayhave other shapes. For example, the spacers 450 may have a circular topview.

Referring to FIG. 1 and FIG. 3G, the method 100 proceeds to step 114where the first substrate 410 is combined with a second substrate 420and a liquid crystal layer 430, thereby obtaining the liquid crystalphase modulation device 400. Herein, the second substrate 420 includes abase substrate 422, a second electrode layer 424, and an alignment layerA2. The second electrode layer 424 is formed over the base substrate 422and covers the active region AA. The alignment layer A2 is formed overthe second electrode layer 424 and rubbed.

As shown in FIG. 3G, a liquid crystal phase modulation device 400 isprovided. The liquid crystal phase modulation device 400 includes thefirst substrate 410, the second substrate 420, the liquid crystal layer430, a sealant 440, the spacers 450, and the alignment layers A1 and A2.The sealant 440 is in the seal region SA and between the first substrate410 and the second substrate 420, and surrounds the liquid crystal layer430. For example, the sealant 440 has inner edges aligned with the edgesEX/EY of the seal region SA (referring to FIG. 3D). The first electrodelayer 414 has first electrodes 414 a in the active region AA, while thesecond electrode layer 424 covers the active region AA.

In the present embodiments, the spacers 450 have a bottom surface 450Badjacent to the first substrate 410 and a top surface 450T adjacent tothe second substrate 420. The bottom surface 450B has a larger area thanthat of the top surface 450T. Each of the spacers 450 has a height takenperpendicular to the first substrate 410 corresponding to the cell gap,such that the cell gap is maintained by the spacers 450.

In some embodiments of the present disclosure, the first substrate 410,the second substrate 420, the liquid crystal layer 430, and the sealant440 of the liquid crystal phase modulation device 400 has aconfiguration similar to the substrate 310, the substrate 320, theliquid crystal layer 330, and the sealant 340 of the reference liquidcrystal phase modulation sample 300. For example, the sealant 440 has athickness equal to that of the sealant 340 of the reference liquidcrystal phase modulation sample 300. A thickness of the substrate410/420 is similar to that of the substrate 310/320. For example, thethickness of the substrate 410/420 is in a range of 0.2 to 0.5millimeters. Through the configuration, by detecting the referenceliquid crystal phase modulation sample 300, an extent of substratebending is measured, and the spacers 450 are distributed in an unevendistribution in response to the substrate, so as to prevent and reducethe substrate bending and keep a cell gap of a liquid-crystal deviceuniform.

In the present embodiments, for realizing an electrically tunable phasemodulation device (e.g., an electrically tunable lens with a tunablefocal length, a electrically tunable grating, or a switch), the liquidcrystal phase modulation device 400 is designed with suitableparameters. For example, a thickness T′ of the liquid crystal layer 430is designed to be in a range of about 10 micrometers to about 50micrometers, such as about 20 micrometers to about 50 micrometers. Ifthe thickness T′ of the liquid crystal layer 430 is less than thethickness range, the device may not provide suitable optical power (e.g.lens power) for realizing phase modulation. If the thickness T′ of theliquid crystal layer 430 is greater the thickness range, the device maytake a long response time to operate and return, which in turn willresult in limited applications. In some embodiments, a width W1 of theelectrodes 414 a is designed to be in a range of about 1 micrometer tohundreds of micrometers, such as about 1 micrometer to about 10micrometers. In some embodiments, a pitch P1 between the electrodes 414a is designed to be in a range of about 1 micrometer to hundreds ofmicrometers, such as about 1 micrometer to about 10 micrometers. Forexample, a length and width of the active area AA may be in a range ofabout 1 inch to about 2 inches.

In some embodiments, plural liquid crystal phase modulation devices 400are stacked for enhancing the optical power (e.g., lens power). Forexample, two to four liquid crystal phase modulation devices 400 arestacked and connected with the active region AA in an overlayingposition. In some embodiments, the stacked liquid crystal phasemodulation devices 400 may share their base substrates with each otherfor reducing the overall thickness.

In some embodiments, the liquid crystal phase modulation device 400 mayfurther includes a light shielding layer having an opening correspondingwith the active area AA. The light shielding layer may expose at least aportion of the active area AA and shield the seal region SA, so as toprevent the sealant 440 from being observed. For example, the opening ofthe light shielding layer has an area equal to that of the active areaAA. The spacers 450 are disposed in the active area AA but not in theseal region SA, and most of the spacers 450 are not covered by the lightshielding layer and may be perceived by users. In some embodiments,fabrication variation may occur at a portion of the active area AAadjacent the seal region SA due to the accuracies of mask alignment andmask dimensions and shadow effect. In some examples, the opening of thelight shielding layer may have an area smaller than that of the activearea AA, such that the light shielding layer further covers the portionof the active area AA adjacent the seal region SA, which in turn willprevent an undesired performance resulted from the fabrication variationfrom being observed.

In some embodiments, the light shielding layer may be between thealignment layer A1 and the dielectric layer 416, between the dielectriclayer 416 and the substrate 412, between the alignment layer A2 and thesecond electrode layer 424, or between the second electrode layer 424and the substrate 422. The light shielding layer has a transmittancelower than 20%. The light shielding layer may be conductive ordielectric materials. For example, in some examples, the light shieldinglayer is made of opaque inks, such as black inks. In some examples, thelight shielding layer is made of metal. In some embodiments, a thicknessof the light shielding layer may be greater than about 500 micrometers.In some embodiments, the configuration of the light shielding layer maybe omitted, and the non-active area (which is out of the active area AA)may be viewed by users.

In some embodiments of the present disclosure, the base substrates 412and 422 may be rigid and/or flexible substrates. For example, the basesubstrates 412 and 422 are made of suitable transparent insulatingmaterials, such as glass, quartz, or polymeric material. The first andsecond electrode layers 414 and 424 may be made of suitable transparentconductive materials, such as indium tin oxide (ITO) or antimony tinoxide (ATO). The dielectric layer 416 is made of silicon oxide, polymer,or other suitable dielectric material. The alignment layers A1 and A2may be made of polyimide.

FIGS. 4A-4C illustrate intermediate stages of a method for fabricating aliquid crystal phase modulation device according to some embodiments ofthe present disclosure. Referring to FIG. 1 and FIG. 4A, the methodproceeds to step 110 where spacers 450 are formed on the secondsubstrate 420, instead of formed on the first substrate 410 as shown byFIG. 3F. The configuration of the second substrate 420 is similar tothose aforementioned, and therefore not repeated herein.

Referring to FIG. 1 and FIG. 4B, the method 100 proceeds to step 112where a rubbing process is performed to the alignment layer A2. In someembodiments, a rubbing cloth 500 held by a roller is used to rub thealignment layer A2 in an alignment direction AD2. In some embodiments,the spacers 450 are designed to have a long axis LA parallel as thealignment direction AD2, for example, as shown by FIGS. 7A and 7B, suchthat the spacers 450 may shelter less area, and the alignment layer A2is rubbed more effectively.

Referring to FIG. 1 and FIG. 4C, the method 100 proceeds to step 114where the second substrate 420 is combined with the first substrate 410and the liquid crystal layer 430, thereby obtaining the liquid crystalphase modulation device 400. The configuration of the first substrate410 is similar to those aforementioned, and therefore not repeatedherein.

As shown in FIG. 4C, a liquid crystal phase modulation device 400 isprovided. The liquid crystal phase modulation device 400 includes thefirst substrate 410, the second substrate 420, the liquid crystal layer430, a sealant 440, the spacers 450, and the alignment layers A1 and A2.The sealant 440 is in the seal region SA and between the first substrate410 and the second substrate 420, and surrounds the liquid crystal layer430. The first electrode layer 414 has first electrodes 414 a in theactive region AA, while the second electrode layer 424 covers the activeregion AA. In the present embodiments, the spacers 450 have a bottomsurface 450B adjacent to the second substrate 420 and a top surface 450Tadjacent to the first substrate 410. The bottom surface 450B has alarger area than that of the top surface 450T. Each of the spacers 450has a height taken perpendicular to the first substrate 410corresponding to the cell gap, such that the cell gap is maintained bythe spacers 450.

Other details of the present embodiments are similar to thoseaforementioned, and not repeated herein.

FIG. 5 is a schematic cross-sectional view of a liquid crystal phasemodulation device 400 according to some embodiments of the presentdisclosure. The present embodiment is similar to the embodiments of FIG.3G and FIG. 4C, and the difference between the present embodiment andthe embodiments of FIG. 3G and FIG. 4C is that: in the presentembodiments, a first portion of the spacers 450 (referred to as spacers450-1 hereinafter) are formed on first substrate 410, while a secondportion of the spacers 450 (referred to as spacers 450-5 hereinafter)are formed on the second substrate 420. For example, the spacers 450-1have a bottom surface 450-1B adjacent to the first substrate 410 and atop surface 450-1T adjacent to the second substrate 420, and the spacers450-5 have a bottom surface 450-5B adjacent to the second substrate 420and a top surface 450-5T adjacent to the first substrate 410. The bottomsurfaces 450-4B and 450-5B have a larger area than that of the topsurfaces 450-4T and 450-5T, respectively. In some embodiments, the sizeor shapes of the spacers 450-4 and 450-5 may be the same or different.Other details of the present embodiments are similar to thoseaforementioned, and not repeated herein.

FIG. 6 is a schematic cross-sectional view of a liquid crystal phasemodulation device 400 according to some embodiments of the presentdisclosure. The present embodiment is similar to the embodiment of FIG.3G, and the difference between the present embodiment and the embodimentof FIG. 3G is that: the first electrode layer 414 has first electrodes414 a in the active region AA, and the second electrode layer 424 hassecond electrodes 424 a in the active region AA. In some embodiments,the first electrodes 414 a and the second electrodes 424 a may have thesame pitch, but it should not limit the scope of the presentembodiments. In some other embodiments, the second electrodes 424 a mayhave a pitch different from that of the first electrodes 414 a. Otherdetails of the present embodiments are similar to those aforementioned,and not repeated herein.

Based on the above discussions, it can be seen that the presentdisclosure offers advantages over liquid crystal devices. It isunderstood, however, that other embodiments may offer additionaladvantages, and not all advantages are necessarily disclosed herein, andthat no particular advantage is required for all embodiments. Oneadvantage is that spacers are distributed in response to the bending ofthe substrate, so as to keep a cell gap of a liquid-crystal deviceuniform. Another advantage is that the shape of the spacers is designedto less influence a rubbing procedure, such that a rubbed alignmentlayer can effectively align the liquid crystal molecules.

Although the present disclosure has been described in considerabledetail with reference to certain embodiments thereof, other embodimentsare possible. Therefore, the spirit and scope of the appended claimsshould not be limited to the description of the embodiments containedherein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentdisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the present disclosurecover modifications and variations of this disclosure provided they fallwithin the scope of the following claims.

What is claimed is:
 1. A method for fabricating a liquid crystal phasemodulation device, comprising: combining a first reference substrate, asecond reference substrate, a reference sealant, and a reference liquidcrystal layer to form a reference liquid crystal phase modulationsample; after combining the first reference substrate, the secondreference substrate, the reference sealant, and the reference liquidcrystal layer to form the reference liquid crystal phase modulationsample, detecting thicknesses of a plurality of portions of thereference liquid crystal layer of the reference liquid crystal phasemodulation sample by a detected apparatus; determining a distributionaccording to the detected thicknesses of the portions of the referenceliquid crystal layer; forming a plurality of first spacers over a firstsubstrate in the determined distribution; and combining the firstsubstrate with a second substrate and a liquid crystal layer to form theliquid crystal phase modulation device, wherein combining the firstsubstrate with the second substrate and the liquid crystal layer to formthe liquid crystal phase modulation device comprises: disposing a devicesealant over the first substrate; and bonding the first substrate andthe second substrate such that the liquid crystal layer and the devicesealant are between the first and second substrates, wherein the devicesealant has a thickness substantially equal to a thickness of thereference sealant of the reference liquid crystal phase modulationsample.
 2. The method of claim 1, further comprising: forming analignment layer over the first substrate and the first spacers afterforming the first spacers; and rubbing the alignment layer in analignment direction.
 3. The method of claim 1, wherein forming the firstspacers is performed such that at least one of the first spacers has afirst length in a first direction and a second length in a seconddirection perpendicular to the first direction, and the first length isgreater than the second length.
 4. The method of claim 3, furthercomprising: forming an alignment layer over the first substrate and thefirst spacers after forming the first spacers; and rubbing the alignmentlayer in an alignment direction, wherein the alignment direction isparallel with the first direction.
 5. The method of claim 4, whereinforming the first spacers is performed such that said at least one ofthe first spacers has a first portion tapering toward the alignmentdirection as viewed from top.
 6. The method of claim 5, wherein formingthe first spacers is performed such that said at least one of the firstspacers has a second portion tapering away from the alignment directionas viewed from top.
 7. The method of claim 1, wherein combining thefirst reference substrate, the second reference substrate, the referencesealant, and the reference liquid crystal layer is performed such thatthe reference liquid crystal phase modulation sample is free of a spacerin the reference liquid crystal layer.
 8. The method of claim 1, whereinthe thickness of the device sealant is in a range from 10 micrometers to50 micrometers, and the thickness of the reference sealant is in a rangefrom 10 micrometers to 50 micrometers.
 9. The method of claim 1, whereinthe first substrate has an active region and a seal region surroundingthe active region, and forming the first spacers in the determineddistribution is performed such that a density of the first spacersbetween a first edge of the active region and a center of the activeregion degrades as approaching the first edge of the active region. 10.The method of claim 9, wherein forming the first spacers in thedetermined distribution is performed such that a density of the firstspacers between a second edge of the active region and the center of theactive region degrades as approaching the second edge of the activeregion, wherein the second edge of the active region is not parallelwith the first edge of the active region.
 11. The method of claim 9,wherein a length or a width of the active region is in a range of 1 inchto 2 inches.
 12. The method of claim 1, wherein the first substrate hasan active region and a seal region surrounding the active region, andforming the first spacers in the determined distribution is performedsuch that a density of the first spacers between an edge of the activeregion and a center of the active region is substantially proportionalto a factor, the factor is represented as PF_(i)+q(100%−PF_(i)), andPF_(i) is inversely proportional to a×FDX_(i)+b, wherein i is a positiveinteger, FDX_(i) is a distance between an i^(th) position of the firstspacers and the edge of the active region, a, b, and q are constants,and q is in a range of 0 to
 1. 13. The method of claim 1, wherein thedetected thicknesses of the portions of the reference liquid crystallayer are in a range from 10 micrometers to 50 micrometers.
 14. Themethod of claim 1, wherein a height of the first spacers is in a rangefrom 10 micrometers to 50 micrometers.
 15. The method of claim 1,further comprising: forming a plurality of second spacers over thesecond substrate in the determined distribution prior to combining thefirst substrate with the second substrate and the liquid crystal layerto form the liquid crystal phase modulation device, wherein a height ofthe second spacers is substantially equal to that of the first spacers.16. The method of claim 15, further comprising: forming an alignmentlayer over the second substrate and the second spacers after forming thesecond spacers; and rubbing the alignment layer in an alignmentdirection.
 17. A method for fabricating a liquid crystal phasemodulation device, comprising: fabricating a reference liquid crystalphase modulation sample by combining a first reference substrate, asecond reference substrate, a reference sealant, and a reference liquidcrystal layer; after fabricating the reference liquid crystal phasemodulation sample by combining the first reference substrate, the secondreference substrate, the reference sealant, and the reference liquidcrystal layer, detecting thicknesses of a plurality of portions of thereference liquid crystal layer of the reference liquid crystal phasemodulation sample by a detected apparatus; determining a distributionaccording to the detected thicknesses of the portions of the referenceliquid crystal layer; forming a plurality of first spacers over a firstsubstrate in the determined distribution; and combining the firstsubstrate, a second substrate, a device sealant, a liquid crystal layerto form the liquid crystal phase modulation device, wherein the devicesealant has a thickness substantially equal to a thickness of thereference sealant.
 18. The method of claim 17, wherein fabricating thereference liquid crystal phase modulation sample is performed such thatthe reference liquid crystal phase modulation sample is free of a spacerin the reference liquid crystal layer.